20,053 research outputs found
A Deep Relevance Matching Model for Ad-hoc Retrieval
In recent years, deep neural networks have led to exciting breakthroughs in
speech recognition, computer vision, and natural language processing (NLP)
tasks. However, there have been few positive results of deep models on ad-hoc
retrieval tasks. This is partially due to the fact that many important
characteristics of the ad-hoc retrieval task have not been well addressed in
deep models yet. Typically, the ad-hoc retrieval task is formalized as a
matching problem between two pieces of text in existing work using deep models,
and treated equivalent to many NLP tasks such as paraphrase identification,
question answering and automatic conversation. However, we argue that the
ad-hoc retrieval task is mainly about relevance matching while most NLP
matching tasks concern semantic matching, and there are some fundamental
differences between these two matching tasks. Successful relevance matching
requires proper handling of the exact matching signals, query term importance,
and diverse matching requirements. In this paper, we propose a novel deep
relevance matching model (DRMM) for ad-hoc retrieval. Specifically, our model
employs a joint deep architecture at the query term level for relevance
matching. By using matching histogram mapping, a feed forward matching network,
and a term gating network, we can effectively deal with the three relevance
matching factors mentioned above. Experimental results on two representative
benchmark collections show that our model can significantly outperform some
well-known retrieval models as well as state-of-the-art deep matching models.Comment: CIKM 2016, long pape
Universality and properties of neutron star type I critical collapses
We study the neutron star axisymmetric critical solution previously found in
the numerical studies of neutron star mergers. Using neutron star-like initial
data and performing similar merger simulations, we demonstrate that the
solution is indeed a semi-attractor on the threshold plane separating the basin
of a neutron star and the basin of a black hole in the solution space of the
Einstein equations. In order to explore the extent of the attraction basin of
the neutron star semiattractor, we construct initial data phase spaces for
these neutron star-like initial data. From these phase spaces, we also observe
several interesting dynamical scenarios where the merged object is supported
from prompt collapse. The properties of the critical index of the solution, in
particular, its dependence on conserved quantities, are then studied. From the
study, it is found that a family of neutron star semi-attractors exist that can
be classified by both their rest masses and ADM masses.Comment: 13 pages, 12 figures, 1 new reference adde
Classification of Overlapped Audio Events Based on AT, PLSA, and the Combination of Them
Audio event classification, as an important part of Computational Auditory Scene Analysis, has attracted much attention. Currently, the classification technology is mature enough to classify isolated audio events accurately, but for overlapped audio events, it performs much worse. While in real life, most audio documents would have certain percentage of overlaps, and so the overlap classification problem is an important part of audio classification. Nowadays, the work on overlapped audio event classification is still scarce, and most existing overlap classification systems can only recognize one audio event for an overlap. In this paper, in order to deal with overlaps, we innovatively introduce the author-topic (AT) model which was first proposed for text analysis into audio classification, and innovatively combine it with PLSA (Probabilistic Latent Semantic Analysis). We propose 4 systems, i.e. AT, PLSA, AT-PLSA and PLSA-AT, to classify overlaps. The 4 proposed systems have the ability to recognize two or more audio events for an overlap. The experimental results show that the 4 systems perform well in classifying overlapped audio events, whether it is the overlap in training set or the overlap out of training set. Also they perform well in classifying isolated audio events
Theory of the "honeycomb chain-channel" reconstruction of Si(111)3x1
First-principles electronic-structure methods are used to study a structural
model for Ag/Si(111)3x1 recently proposed on the basis of transmission electron
diffraction data. The fully relaxed geometry for this model is far more
energetically favorable than any previously proposed, partly due to the unusual
formation of a Si double bond in the surface layer. The calculated electronic
properties of this model are in complete agreement with data from
angle-resolved photoemission and scanning tunneling microscopy.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Lett (the ugly postscript
error on page 4 has now been repaired
A New Non-Abelian Topological Phase of Cold Fermi Gases in Anisotropic and Spin-Dependent Optical Lattices
To realize non-Abelian s-wave topological superfluid (TS) of cold Fermi
gases, generally a Zeeman magnetic field larger than superfluid pairing gap is
necessary. In this paper we find that using an anisotropic and spin-dependent
optical lattice (ASDOL) to trap gases, a new non-Abelian TS phase appears, in
contrast to an isotropic and spin-independent optical lattice. A characteristic
of this new non-Abelian TS is that Zeeman magnetic field can be smaller than
the superfluid pairing gap. By self-consistently solving pairing gap equation
and considering the competition against normal state and phase separation, this
new phase is also stable. Thus an ASDOL supplies a convenient route to realize
TS. We also investigate edge states and the effects of a harmonic trap
potential
Fluctuation of Conductance Peak Spacings in Large Semiconductor Quantum Dots
Fluctuation of Coulomb blockade peak spacings in large two-dimensional
semiconductor quantum dots are studied within a model based on the
electrostatics of several electron islands among which there are random
inductive and capacitive couplings. Each island can accommodate electrons on
quantum orbitals whose energies depend also on an external magnetic field. In
contrast with a single island quantum dot, where the spacing distribution is
close to Gaussian, here the distribution has a peak at small spacing value. The
fluctuations are mainly due to charging effects. The model can explain the
occasional occurrence of couples or even triples of closely spaced Coulomb
blockade peaks, as well as the qualitative behavior of peak positions with the
applied magnetic field.Comment: 13 pages, 4 figures, accepted for publication in PR
Can degenerate bound states occur in one dimensional quantum mechanics?
We point out that bound states, degenerate in energy but differing in parity,
may form in one dimensional quantum systems even if the potential is
non-singular in any finite domain. Such potentials are necessarily unbounded
from below at infinity and occur in several different contexts, such as in the
study of localised states in brane-world scenarios. We describe how to
construct large classes of such potentials and give explicit analytic
expressions for the degenerate bound states. Some of these bound states occur
above the potential maximum while some are below. Various unusual features of
the bound states are described and after highlighting those that are ansatz
independent, we suggest that it might be possible to observe such parity-paired
degenerate bound states in specific mesoscopic systems.Comment: 10 pages, 2 figures, to appear in Europhysics Letter
- …